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SubjectRe: [RFC PATCH V3 12/21] mmc: sdhci: UHS-II support, add hooks for additional operations
Adrian, Ben,

Regarding _reset() function,

On Fri, Aug 21, 2020 at 05:08:32PM +0300, Adrian Hunter wrote:
> On 10/07/20 2:10 pm, Ben Chuang wrote:
> > From: Ben Chuang <ben.chuang@genesyslogic.com.tw>
> >
> > In this commit, UHS-II related operations will be called via a function
> > pointer array, sdhci_uhs2_ops, in order to make UHS-II support as
> > a kernel module.
> > This array will be initialized only if CONFIG_MMC_SDHCI_UHS2 is enabled
> > and when the UHS-II module is loaded. Otherwise, all the functions
> > stay void.
> >
> > Signed-off-by: Ben Chuang <ben.chuang@genesyslogic.com.tw>
> > Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> > ---
> > drivers/mmc/host/sdhci.c | 152 ++++++++++++++++++++++++++++++++++-----
> > 1 file changed, 136 insertions(+), 16 deletions(-)
> >

(snip)

> > if (host->ops->platform_send_init_74_clocks)
> > host->ops->platform_send_init_74_clocks(host, ios->power_mode);
> >
> > @@ -2331,7 +2411,7 @@ void sdhci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
> > }
> >
> > if (host->version >= SDHCI_SPEC_300) {
> > - u16 clk, ctrl_2;
> > + u16 clk;
> >
> > if (!host->preset_enabled) {
> > sdhci_writeb(host, ctrl, SDHCI_HOST_CONTROL);
> > @@ -3173,11 +3253,19 @@ static bool sdhci_request_done(struct sdhci_host *host)
> > /* This is to force an update */
> > host->ops->set_clock(host, host->clock);
> >
> > - /* Spec says we should do both at the same time, but Ricoh
> > - controllers do not like that. */
> > - sdhci_do_reset(host, SDHCI_RESET_CMD);
> > - sdhci_do_reset(host, SDHCI_RESET_DATA);
> > -
> > + if (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> > + host->mmc->flags & MMC_UHS2_INITIALIZED) {
> > + if (sdhci_uhs2_ops.reset)
> > + sdhci_uhs2_ops.reset(host,
> > + SDHCI_UHS2_SW_RESET_SD);
> > + } else {
> > + /*
> > + * Spec says we should do both at the same time, but
> > + * Ricoh controllers do not like that.
> > + */
> > + sdhci_do_reset(host, SDHCI_RESET_CMD);
> > + sdhci_do_reset(host, SDHCI_RESET_DATA);
> > + }
>
> Please look at using the existing ->reset() sdhci host op instead.

Well, the second argument to those reset functions is a bit-wise value
to different "reset" registers, SDHCI_SOFTWARE_RESET and SDHCI_UHS2_SW_RESET,
respectively.

This fact raises a couple of questions to me:

1) Does it make sense to merge two functionality into one, i.e.
sdhci_do_reset(), which is set to call ->reset hook?

-> Adrian

2) UHS2_SW_RESET_SD is done only at this place while there are many callsites
of reset(RESET_CMD|RESET_DATA) in sdhci.c.
Why does the current code work?

I found, in sdhci-pci-gli.c,
sdhci_gl9755_reset()
/* reset sd-tran on UHS2 mode if need to reset cmd/data */
if ((mask & SDHCI_RESET_CMD) | (mask & SDHCI_RESET_DATA))
gl9755_uhs2_reset_sd_tran(host);

Is this the trick to avoid the issue?
(It looks redundant in terms of the hack above in sdhci_request_done()
and even quite dirty to me. Moreover, no corresponding code for gl9750
and gl9763.)

-> Ben

3) (More or less SD specification issue)
In UHS-II mode, do we have to call reset(SHCI_RESET_ALL) along with
reset(UHS2_SW_RESET_FULL)?
Under the current implementation, both will be called at the end.

-> Adrian, Ben

4) (Not directly linked to UHS-II support)
In some places, we see the sequence:
sdhci_do_reset(host, SDHCI_RESET_CMD);
sdhci_do_reset(host, SDHCI_RESET_DATA);
while in other places,
sdhci_do_reset(host, SDHCI_RESET_CMD | SDHCI_RESET_DATA);

If the statement below is true,
> > - /* Spec says we should do both at the same time, but Ricoh
> > - controllers do not like that. */
the latter should be wrong.

-> Adrian

-Takahiro Akashi



> > host->pending_reset = false;
> > }
> >
> > @@ -3532,6 +3620,13 @@ static irqreturn_t sdhci_irq(int irq, void *dev_id)
> > SDHCI_INT_BUS_POWER);
> > sdhci_writel(host, mask, SDHCI_INT_STATUS);
> >
> > + if (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> > + intmask & SDHCI_INT_ERROR &&
> > + host->mmc->flags & MMC_UHS2_SUPPORT) {
> > + if (sdhci_uhs2_ops.irq)
> > + sdhci_uhs2_ops.irq(host);
> > + }
> > +
>
> Please look at using the existing ->irq() sdhci host op instead
>
> > if (intmask & (SDHCI_INT_CARD_INSERT | SDHCI_INT_CARD_REMOVE)) {
> > u32 present = sdhci_readl(host, SDHCI_PRESENT_STATE) &
> > SDHCI_CARD_PRESENT;
> > @@ -4717,6 +4812,14 @@ int sdhci_setup_host(struct sdhci_host *host)
> > /* This may alter mmc->*_blk_* parameters */
> > sdhci_allocate_bounce_buffer(host);
> >
> > + if (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> > + host->version >= SDHCI_SPEC_400 &&
> > + sdhci_uhs2_ops.add_host) {
> > + ret = sdhci_uhs2_ops.add_host(host, host->caps1);
> > + if (ret)
> > + goto unreg;
> > + }
> > +
>
> I think you should look at creating uhs2_add_host() instead
>
> > return 0;
> >
> > unreg:
> > @@ -4738,6 +4841,8 @@ void sdhci_cleanup_host(struct sdhci_host *host)
> > {
> > struct mmc_host *mmc = host->mmc;
> >
> > + /* FIXME: Do we have to do some cleanup for UHS2 here? */
> > +
> > if (!IS_ERR(mmc->supply.vqmmc))
> > regulator_disable(mmc->supply.vqmmc);
> >
> > @@ -4766,6 +4871,14 @@ int __sdhci_add_host(struct sdhci_host *host)
> > mmc->cqe_ops = NULL;
> > }
> >
> > + if ((mmc->caps & MMC_CAP_UHS2) && !host->v4_mode) {
> > + /* host doesn't want to enable UHS2 support */
> > + mmc->caps &= ~MMC_CAP_UHS2;
> > + mmc->flags &= ~MMC_UHS2_SUPPORT;
> > +
> > + /* FIXME: Do we have to do some cleanup here? */
> > + }
> > +
> > host->complete_wq = alloc_workqueue("sdhci", flags, 0);
> > if (!host->complete_wq)
> > return -ENOMEM;
> > @@ -4812,6 +4925,9 @@ int __sdhci_add_host(struct sdhci_host *host)
> > unled:
> > sdhci_led_unregister(host);
> > unirq:
> > + if (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> > + sdhci_uhs2_ops.remove_host)
> > + sdhci_uhs2_ops.remove_host(host, 0);
> > sdhci_do_reset(host, SDHCI_RESET_ALL);
> > sdhci_writel(host, 0, SDHCI_INT_ENABLE);
> > sdhci_writel(host, 0, SDHCI_SIGNAL_ENABLE);
> > @@ -4869,6 +4985,10 @@ void sdhci_remove_host(struct sdhci_host *host, int dead)
> >
> > sdhci_led_unregister(host);
> >
> > + if (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> > + sdhci_uhs2_ops.remove_host)
> > + sdhci_uhs2_ops.remove_host(host, dead);
> > +
>
> I think you should look at creating uhs2_remove_host() instead
>
> > if (!dead)
> > sdhci_do_reset(host, SDHCI_RESET_ALL);
> >
> >
>

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